[R-390] Slide rule calculations

[w9ya]

Hey Bill and the gang;

Actually the log-log scales were PERFECT for computing complex interest, and
bankers often used slide rules with scales of this sort.

(And yes it IS possible to get 5 orders of magnitude accuracy from a slide
rule. Yeah I know the popular way things were taught did not acheive this
accuracy, but the way things are taught does not limit what is possible by
using other techniques.)

On a slightly different vein here's a good trivia question;

"Who invented the log-log scales ?" They were first proposed by a fellow
named Roget. The SAME Roget from Thesaurus fame !!

Vy 73;

Bob
w9ya


On Fri, Dec 5, 2008 at 6:20 PM, Bill Hawkins <bill at iaxs.net> wrote:

> Well, slide rules never caught on at banks. They are excellent for
> engineering
> estimates, where reality restricts us to 3-4 significant digits. Why the
> restriction? That was the accuracy of engineering measurements at the
> time.
>
> There's no fixed rule that results in 1/3 being zero. If the situation
> is
> such that only integers count, then 1/3 is zero. If the situation
> requires
> three digits to the right of the decimal point, then 1/3 is 0.333.
>
> Our R-390 class sets have 5 digit accuracy, with 3 digits to the right
> of
> the decimal. You can tune closer than that with a calibrated BFO.
>
> Bill Hawkins
>
>
> -----Original Message-----
> From: Barry
>
> > In the end, 3.12/9.7 is NOT 0.321649484536....    It is 0.32.  Digits
>
> > of precision in = digits of precision out.  This, of course, applies
> > equally to sliderule calculations,  electronic calculator thingies, or
>
> > computers with 128-bit  or more floating point arithmetic.
> >
> > Grant/NQ5T
>
> That's one of those rules that I first came across in college physics
> class
> and I struggled with it then as now.
>
> I understand basically why it is used, but by the same rule, is 1/3=0?
>
> Barry - N4BUQ
>
>
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